[PATCH] block: fix potential invalid pointer dereference in blk_add_partition

[PATCH] block: fix potential invalid pointer dereference in blk_add_partition

[Riyan Dhiman]

The blk_add_partition() function initially used a single if-condition
(IS_ERR(part)) to check for errors when adding a partition. This was
modified to handle the specific case of -ENXIO separately, allowing the
function to proceed without logging the error in this case. However,
this change unintentionally left a path where md_autodetect_dev()
could be called without confirming that part is a valid pointer.

This commit separates the error handling logic by splitting the
initial if-condition, improving code readability and handling specific
error scenarios explicitly. The function now distinguishes the general
error case from -ENXIO without altering the existing behavior of
md_autodetect_dev() calls.

Fixes: b72053072c0b (block: allow partitions on host aware zone devices)

Signed-off-by: Riyan Dhiman <riyandhiman14@gmail.com>
---
Compile tested only

 block/partitions/core.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/block/partitions/core.c b/block/partitions/core.c
index ab76e64f0f6c..5bd7a603092e 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -555,9 +555,11 @@ static bool blk_add_partition(struct gendisk *disk,
 
 	part = add_partition(disk, p, from, size, state->parts[p].flags,
 			     &state->parts[p].info);
-	if (IS_ERR(part) && PTR_ERR(part) != -ENXIO) {
-		printk(KERN_ERR " %s: p%d could not be added: %pe\n",
-		       disk->disk_name, p, part);
+	if (IS_ERR(part)) {
+		if (PTR_ERR(part) != -ENXIO) {
+			printk(KERN_ERR " %s: p%d could not be added: %pe\n",
+			       disk->disk_name, p, part);
+		}
 		return true;
 	}
 
-- 
2.46.0

Re: [PATCH] block: fix potential invalid pointer dereference in blk_add_partition

[Bart Van Assche]

On 9/8/24 10:10 AM, Riyan Dhiman wrote:
> The blk_add_partition() function initially used a single if-condition
> (IS_ERR(part)) to check for errors when adding a partition. This was
> modified to handle the specific case of -ENXIO separately, allowing the
> function to proceed without logging the error in this case. However,
> this change unintentionally left a path where md_autodetect_dev()
> could be called without confirming that part is a valid pointer.
> 
> This commit separates the error handling logic by splitting the
> initial if-condition, improving code readability and handling specific
> error scenarios explicitly. The function now distinguishes the general
> error case from -ENXIO without altering the existing behavior of
> md_autodetect_dev() calls.
> 
> Fixes: b72053072c0b (block: allow partitions on host aware zone devices)
> 
> Signed-off-by: Riyan Dhiman <riyandhiman14@gmail.com>

No blank line between the Fixes: and Signed-off-by: tags please.
Additionally, please Cc the author of a patch when posting a fix for a
patch.

Thanks,

Bart.